ABSTRACT- Sediment is both a physically and chemically complex matrix. This complexity places distinct limits on the use of analytical chemistry to estimate the bioavailability and toxicity of contaminants present in dredged material. Biological testing is widely accepted as a definitive method for characterizing the chemical hazards in dredged material. By exposing relevant organisms under controlled conditions to samples of the actual material to be dredged and measuring either the bioaccumulation of contaminants into tissues or toxicological effects in the test organisms (e.g., mortality) conclusions can be reached about the presence of chemical hazards. Such methods provide a direct and definitive approach for assessing sediment. In 2001, the International Navigation Association (PIANC) established a working group with members from nine countries to develop technical guidance for the use of biological testing to make decisions about managing sediment dredged to support navigation. The developed guidance describes the use of methods for assessing the bioavailability of sediment-associated contaminants through the use of bioaccumulation tests and acute and chronic toxicity tests. Generic guidance for developing such tests with species of regional relevance is discussed. Guidelines for selection and use of reference sediment as a basis for comparison during testing is described. A decision-making framework based on the use of multiple lines-of-evidence is proposed for evaluating biological test data and integrating these data to reach conclusions about exposure, effects and risk.